EP1263122A1 - Linear drive having a rotational symmetry and a double-sided actuator arrangement - Google Patents

Abstract

The linear drive has an electromagnetically-controlled cylindrical rotor (8) provided with permanent magnets (2) and a cylindrical stator (7) provided with a single- or multi-phase winding (3). Either the stator or the rotor is provided as a double-sided actuator with a cylindrical inner part (5) and a cylindrical outer part (4) having aligned poles.

Description

The invention relates to a linear drive according to the preamble of the claim 1, which in particular for stroke control of a gas exchange play Internal combustion engine is used.

There are various configurations for valve control in internal combustion engines known from the prior art. For example, DE 195 18 056 A1 a gas valve control with a gas exchange valve known by an electromagnet arrangement is actuated. Big problems when using a Electromagnetic arrangement for actuating the valve represent the high level of noise when reaching the respective end positions, the abrupt braking when reaching the end positions, as well as the required high holding currents.

From the publications DE 42 17 357 C2, DE 197 23 923 A1, DE 197 51 176 A1 and EP 0 390 519 B1, a linear drive of the type mentioned at the beginning is known. The disclosed valve arrangements are concentric in a stator arranged electric rotor, which is coupled to a valve member and operated this.

For example, the linear drive shown in DE 42 17 357 C2 includes one cylindrical air gap and annular coils in slots of the stator, the Stand washers, which alternate with the coils in a layering, and a outside stator yoke and the rotor has ring washers. The washers of the runner alternate in a layering with conductor rings, the Ring washers and an inner runner yoke the grooves for the conductor rings form. This arrangement enables an axially compact structure to be achieved.

The linear drive disclosed in DE 197 23 923 A1 serves in a valve arrangement as an actuator for a valve member, and has a rotor coupled to the valve member on, the stand being constructed from sheet metal, the surface of which is perpendicular to the Direction of movement of the rotor is oriented, and the stand facing the rotor Has teeth, each a closed, facing the rotor Have lateral surface. This arrangement enables a small pole pitch and thus a high force density and precise force adjustment along the stroke.

The linear drive known from DE 197 51 176 A1 comprises a in a bearing guided coil-like carriage, the bearing a radially magnetized Has ring magnets. This will result in an enhanced magnetic effect by far extended slide achieved so that a faster stroke movement can be achieved is.

The linear drive according to EP 0 390 519 B1 consists of one with a valve coupled movable ring-shaped permanent magnets with axially offset Pole made by a coil assembly with fixed axially spaced magnetic poles is surrounded. The coil arrangement is designed so that there is a high driving force at the beginning of the valve opening process and at the end of the valve closing process results.

With the aforementioned linear drives, however, there is a frictional or stop-related Wear due to the operational conditions that affect the windings Jarring. In addition, the noise development is remarkable.

DE 199 10 065 C1 also discloses a linear drive of the type mentioned at the beginning Type in which the stand is surrounded by at least two coaxially surrounding one another, formed as a polygonal hollow iron sheet stack, the sheets are oriented essentially transversely to the direction of movement of the rotor. The Rotor is a hybrid rotor coupled to a valve member of a control valve assembly and essentially has at least two spaced coaxially surrounding one another formed from iron sheet polygon hollow cylinder, these and the hollow cylindrical sheet metal stack of the stand, forming one each Interlocking air gap at least partially surround each other. The polygon cylindrical shape allows easy manufacture and assembly of the linear drive. Furthermore, the multi-part concentric arrangement of the stator windings enables a reduction in the vibrating forces acting on the windings, causing vibrations the windings or friction on the sheets are reduced.

With the aforementioned linear drive based on the reluctance effect multi-part stator is not, for example, for valve control at high The required force, dynamics and installation space can be reached to keep a valve inside to open a maximum available time against an existing gas pressure.

It is therefore an object of the present invention to be low-wear and quiet To provide linear drive with improved power and dynamics.

This object is achieved according to claim 1 in that the cylindrical Runner has a rotationally symmetrical shape with radially magnetized permanent magnets and that the stator or the rotor as one of a cylindrical Inner part and a cylindrical outer part facing each other in alignment arranged active poles existing double-sided actuator arrangement is formed is.

By using radially magnetized permanent magnets and by the double-sided actuator arrangement caused double air gap on the moving Permanent magnets result in an increase in force with less movement Dimensions. Furthermore, the rotationally symmetrical structure leads due to its rotatability in connection with the non-stop due to the use of the synchronous principle The nature of the linear drive to reduce wear and friction. In addition, no initial adjustment is required. Because the linear actuator shows linear system behavior and the synchronous principle allows a variable stroke, sensorless control is also possible.

The double-sided actuator arrangement can alternatively be a combination of Indoor and outdoor stands with runners arranged in between or by one Combination of inner and outer runners with stand in between be designed. The permanent magnets are preferably ring magnets or Axial permanent magnets designed. The single or multi-phase winding or Windings can be designed as slot-tooth or air gap windings. Either the cylindrical rotor as well as the cylindrical stand can be made of a sheet metal or massive soft magnetic material.

According to an advantageous development, the permanent magnets are alternating Magnetic poles arranged.

According to another advantageous development, the inner and outer parts have different radial dimensions. It is also possible that the moving Part is not arranged centrally between the inner and outer part. Through one asymmetrical structure can facilitate the dissipation of the heat loss.

According to a further advantageous development, the rotor has a cup-shaped one Carrier on whose cylindrical carrier jacket ring magnets are attached, wherein the carrier jacket is formed from a non-magnetic material.

As an advantageous further development, the rotor can also take place at every second pole of a permanent magnet have a soft magnetic material, whereby Magnetic material can be saved.

The linear drive can be used, for example, as a stroke actuator for a gas interaction of an internal combustion engine or as an active spring-damper element and / or as an adjusting element be designed for an active vehicle chassis.

The invention is described below using an exemplary embodiment with reference explained in more detail on the drawing. The only drawing figure shows one Valve arrangement with a rotationally symmetrical electric linear drive schematically in longitudinal section. According to the exemplary embodiment, the linear drive as an actuator for a valve member of a valve-controlled internal combustion engine used.

The valve arrangement shown in the figure shows only the drive part and the Valve element 1 for the valve-controlled internal combustion engine. The one for understanding parts of the valve arrangement and the internal combustion engine which are not further relevant to the invention are not further illustrated for reasons of clarity.

The internal combustion engine has a combustion cylinder (not shown) on the at least one control valve arrangement with an electric linear drive is arranged according to the figure as an actuator for the valve member 1. The Linear drive has a cup-shaped coupling coupled to the valve rod of valve member 1 Runner 8 on between a laminated or massive outer Stand 4 and a laminated or solid inner stand 5 movable is led. Thus, a two-part stator arrangement 7 is a double-sided actuator arrangement educated. The linear drive is rotationally symmetrical to an axis of symmetry 11 trained.

According to the illustration in the figure, the inner is designed as a hollow cylinder Stand 5 fixed on a carrier shaft 10 and has grooves and teeth. Also the with the inner stand 5 rigidly coupled outer stand 4 has corresponding Teeth and grooves on the teeth and grooves of the inner stand 5 radially face in alignment, with the runner 8 being guided between them. In the outer and inner stator slots are ring-shaped windings 3. The cup-shaped Runner 8 consists of a preferably non-magnetic cylindrical Rotor back 6 with a base plate 9, which is coupled to the valve member 1, so that the lifting movement of the rotor 8 is transmitted to the valve member 1. At the The inside of the rotor back 6 are designed as radially magnetized ring magnets Permanent magnets 2 attached, their axial length and axial distance depends on the selected pole pitch τp and pole coverage ατp. Between the inner surface of the outer stand 4 and the outer surface of the rotor 8, an outer air gap L1 is formed. Furthermore, there is an inner air gap L2 between the outer surface of the inner stand 5 and the inner surface of the runner 8 formed.

The following are specific design options of the in the figure shown linear actuator for a force development of more than 600N at one Stroke from 8 to 10mm, a valve mass of 60g, a duration of the opening process (5% to 95% of the stroke) of 3ms, a nominal voltage of 42V and one maximum permissible peak current of 30A is shown.

The course of acceleration is preferably trapezoidal, thus abrupt, for Vibrational excitation leading force changes can be avoided. The linear drive must be designed so that it is the sum of the required acceleration force and can apply the valve force in both stroke directions. Therefore the total force required increases to approx. 700N. The switched by a Reluctance actuator achievable force per axial length is the same Construction volume and the same current density significantly below that shown in the figure permanently excited brushless actuator. In addition, the single-phase variant force of the reluctance actuator is only possible in one direction. To minimize The size of the linear drive is therefore the permanently excited brushless Actuator used. The double-sided actuator arrangement, for example with the in the Figure shown inner and outer stands 5, 4 leads to increased by about 25% Force values compared to a one-sided actuator arrangement with an internal one Stand and same geometry.

A single-phase configuration in which the stator windings 3 have only one AC phase has the advantage that the current is in phase when moving Runner 8 does not have to reverse its direction. Disadvantageous compared to one multi-phase design, however, are due to the higher magnetic Backflow required larger construction volume or the reduced force with the same Volume.

By using several phases, the rotor poles can be placed side by side be arranged, it must be ensured that the current direction is adapted to the polarity of the rotor magnetic field. Therefore a current reversal is in the phases depending on the rotor movement required. There is also a position signal of the rotor 8 relative to the stator assembly 7 required to the Current amount and the current direction can be set accordingly.

Soft magnetic materials such as special alloys (eg Vacoflux 17) made of sintered material, powder iron materials, structural steel (St37) or standard electrical sheets can be used as the stand material. It should be taken into account that the sintered material such as Vacoflux 17, due to its highest saturation flux density, can achieve the highest force effect. Hard magnetic materials, for example made of samarium cobalt (Sm ₂ Co17) or from temperature-stabilized neodymium iron drilling (NdFeB) can be used for the magnetic material of the permanent magnets 2. To save the required amount of magnetic material, the permanent material of the permanent magnets 2 at every second rotor pole can be replaced by soft magnetic material, so that a permanent magnet 2 is only provided at every second rotor pole. However, the achievable force is reduced to approx. 75% of the force with full magnet use.

The carrier shaft 10 and the inner stand 5 can be combined and made of full material (e.g. mild steel St37). Alternatively, the carrier wave 10 made of structural steel and the inner stand 5 made of Trafoperm or Vacoflux rings be made, which reduces eddy currents and mechanical properties be improved. The rotor back 6 can be made of a non-magnetic Steel pipe be formed. The outer stand 4 can be made of Trafoperm or Vacoflux washers or be constructed from a powder composite.

An example of how to implement the above specifications is given for the concrete dimension values a radius of the carrier shaft 10 of 3.7 mm, one radial height of the stator back of 0.8 mm, a radial height of the rotor back 6 of 0.5mm, a radial depth of the stud grooves of 4.8mm, an axial width of the Stand teeth of 0.9mm, axial width of the stand grooves of 2.1mm, a radial Magnet height of the permanent magnets 2 of 1.3 mm, a pole coverage factor α of 0.875, a pole pitch τp of 9mm, a mechanical air gap (L1 or L2) of 0.5mm (with centered magnetic rotor back 6) and an axial length of 108mm.

The pole pitch can preferably be selected as a multiple of the range of motion so that there is no unnecessary overhang at the ends (edge poles). little one Pole pitches are advantageous because they reduce the necessary height of the rotor back 6 and the stand back and allow local saturation effects then only negligible due to the shorter return path lengths cause magnetic voltages.

The stator teeth are required to guide the river. But with an increase the tooth width of the space available for the windings 3 smaller. The relationship between stator tooth width and pole pitch τp should be for a optimal force development be about 0.3. The groove depth is determined by the Height of the stator back dependent magnetic saturation of the stator back limited. The stator tooth height thus results from the specified stator back height and the predetermined outer diameter of the formed as magnetic rings Permanent magnets 2.

The fill factor of the windings 3 is due to the necessary conductor insulation and the winding technology used (manual or automatic winding) less than 1. Also Cross connections must be provided when using ring windings that take up part of the groove volume. It can therefore be an actual one Current load of the winding conductor determining fill factor from 0.4 to Realize 0.6.

Two phases are sufficient to generate a moving field in the stand 8, the number of holes (slots per pole and phase) is increased (e.g. from 1 to 2). The Usage increases, for example, from 9 (3 stator poles and 3 slots per pole) to 12 (three Stator poles and 4 slots per pole). The tooth and groove width must be appropriate be adjusted.

The linear drive can be used as a pure linear actuator, as a spring-linear actuator-holding system combination with a spring (e.g. with a progressive characteristic) as an energy store when opening the valve member 1, the tensioned when closing the valve is, the holding system, for example formed by a coil arrangement to keep the spring preload low-current without activating the linear actuator serves, or as a solenoid-linear actuator combination with a solenoid system to open and accelerate the valve member 1, the linear actuator then takes over the acceleration process.

With a pure linear actuator, at least for the aforementioned requirements 11 rotor poles required. The linear actuator must be used for spring support For example, only apply half of the total force required so that at least 5 rotor poles are required with a correspondingly reduced rotor length. In the case of a single-layer ring winding, according to W. Deleroi, "influence of the stator winding arrangement on the operating behavior of asynchronous linear motors ", ETZ-A, Vol. 95, pp. 601-606, 1974 a straight stator pole number advantageous. Therefore in both cases the number of stator poles is preferably increased by one pole, so that 12 stator poles for the pure linear actuator and 6 stator poles for the linear actuator with spring support.

Deviating from the symmetrical construction of the linear drive shown in the figure an asymmetrical structure is also possible, in which the radial dimensions of the inner and outer stands 5, 4 differ from each other. Will be there the groove depth of the inner stand 5 is chosen greater than the groove depth of the outer Stand, there is an advantageous shift in the generation of heat loss to the outer stand 4, where it can be easily removed. The asymmetrical The structure can be determined, for example, by specifying certain magnetic ring dimensions be conditional. For both types of construction, a high number of turns with small Conductor cross section or a low number of turns with a large conductor cross section to get voted. For the symmetrical structure, a high number of turns of 20 and a low number of turns of 12 on the inner and outer stands 5, 4 to get voted. A high number of turns can be used for the asymmetrical structure of 16 and a low number of turns of 9 on the inner stand 5 and a high one Number of turns of 32 and a low number of turns of 18 on the outer stand 4 can be selected, the inner stand 5, for example, a groove depth of 4.1 mm and the outer stand 4, for example, has a groove depth of 6.1 mm.

The rotor back 6 can also be arranged centrally, on both sides Permanent magnets 2 are attached and the rotor back 6 made of magnetic Material exists. The arrangement of the rotor back 6 shown in the figure on the outer edge of the runner 8, on the one hand, enables an external bearing surface and on the other hand halving the number of required permanent magnets 2. However, the rotor back 6 must then be non-magnetic. This disadvantage can be reduced by taking the inner air gap L2 from 0.5mm to 0.3mm and by Reduction of the outer air gap L1 from 0.5mm to 0.2mm can be compensated.

As an alternative to the embodiment described above according to the Representation in the figure is the double-sided actuator structure with two air gaps also by providing an inner and outer rotor with an intermediate one Stand can be realized. In this case, the valve member 1 is with the inner and / or outer runners coupled. The inner and outer runners point to theirs Radially magnetized permanent magnet poles facing each other on the inside on.

The dimensions mentioned in the embodiment described above are used only to illustrate the geometry of the linear drive for a specific individual case. Of course, the linear drive different dimensions depending on the individual performance requirements, Have materials, pole and / or number of turns. The concrete design the linear drive can be modified within the scope of the claims become.

Claims (10)

Electric linear drive, in particular for stroke control of a gas exchange play of an internal combustion engine, with an electromagnetically controllable and movably arranged cylindrical rotor (8) and a cylindrical stator (7), each with a single or multi-phase winding or windings (3), characterized in that the cylindrical Rotor (8) has a rotationally symmetrical shape with magnetized permanent magnets (2), and that the stator (7) or the rotor (8) as one of a cylindrical inner part (5) and a cylindrical outer part (4) with active poles arranged flush with one another existing double-sided actuator arrangement is formed. Electric linear drive according to claim 1, characterized in that the permanent magnets (2) are designed as surface-mounted ring magnets or axial permanent magnets. Electric linear drive according to one of claims 1 or 2, characterized in that the single-phase or multi-phase winding or windings (3) are designed as slot-tooth or air-gap winding. Electric linear drive according to one of claims 1 to 3, characterized in that both the cylindrical rotor (8) and the cylindrical stator (7) are formed in one piece from a laminated or solid soft magnetic material. Electric linear drive according to one of claims 1 to 4, characterized in that the permanent magnets (2) are arranged with alternating magnetic poles. Electric linear drive according to one of claims 1 to 5, characterized in that the inner and outer part have different radial dimensions. Electric linear drive according to one of claims 1 to 6, characterized in that the rotor (6) has a cup-shaped carrier (6, 9), on the cylindrical carrier jacket (6) ring magnets (2) are fastened, the carrier jacket (6) a non-magnetic material is formed. Electric linear drive according to one of claims 1 to 7, characterized in that the rotor (8) has a soft magnetic material at every second pole instead of a permanent magnet (2). Electric linear drive according to one of claims 1 to 6, characterized in that the linear drive is designed as a stroke actuator for a gas interplay of an internal combustion engine. Electric linear drive according to one of claims 1 to 6, characterized in that the linear drive is designed as an active spring-damper element and / or as an adjusting element for an active vehicle chassis.

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